Particle System component in Unity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Particle System emission rate code?

Consider this Unity C# script snippet that modifies a Particle System's emission rate over time. What will be the emission rate after 3 seconds?

Unity

using UnityEngine;

public class ParticleEmissionTest : MonoBehaviour
{
    public ParticleSystem ps;

    void Start()
    {
        var emission = ps.emission;
        emission.rateOverTime = 10f;
    }

    void Update()
    {
        var emission = ps.emission;
        emission.rateOverTime = 10f + Time.time * 5f;
    }
}

A 10 particles per second

B 15 particles per second

C 25 particles per second

D 30 particles per second

💡 Hint

Remember that Time.time gives the time in seconds since the game started.

The emission rate starts at 10 and increases by 5 every second. After 3 seconds, it is 10 + 3*5 = 25.

🧠 Conceptual

intermediate

Which property controls the shape of particle emission?

In Unity's Particle System component, which property lets you change the shape from which particles are emitted?

A shape.shapeType

B shape.enabled

C main.startSize

D emission.rateOverTime

💡 Hint

Think about the module that defines the geometry of emission.

The shape.shapeType property controls the emission shape like cone, sphere, or box.

🔧 Debug

advanced

Why does this Particle System not emit particles?

Look at this code snippet. The Particle System does not emit any particles when the game runs. What is the cause?

Unity

using UnityEngine;

public class ParticleDebug : MonoBehaviour
{
    public ParticleSystem ps;

    void Start()
    {
        var emission = ps.emission;
        emission.enabled = false;
        ps.Play();
    }
}

A The Particle System variable ps is not assigned.

B Emission is disabled, so no particles are emitted.

C Particle System is not playing because Play() is called in Start().

D The emission rate is zero by default.

💡 Hint

Check the emission module's enabled state.

Disabling emission stops particles from spawning even if Play() is called.

📝 Syntax

advanced

Which code correctly sets the start color of a Particle System?

Choose the correct code snippet to set the start color of a Particle System to red.

A

var main = ps.main;
main.startColor = Color.red;

B

var main = ps.main;
main.startColor = new Color(1, 0, 0);

C ps.main.startColor = Color.red;

D ps.startColor = Color.red;

💡 Hint

The main module is a struct; you must assign its properties correctly.

You must get the main module, then assign startColor using a new Color instance. Option A correctly assigns startColor. Option A misses that main is a struct and needs a local variable, but the new Color instance is correct. Option A and C are incorrect because startColor is not a direct property of ParticleSystem.

🚀 Application

expert

How to smoothly increase particle size over lifetime?

You want particles to start small and grow bigger smoothly as they live. Which code snippet achieves this effect?

A

var main = ps.main;
main.startSize = 1f;
var sizeOverLifetime = ps.sizeOverLifetime;
sizeOverLifetime.enabled = true;
sizeOverLifetime.size = new ParticleSystem.MinMaxCurve(1f, AnimationCurve.Linear(0, 1f, 1, 2f));

B

var sizeOverLifetime = ps.sizeOverLifetime;
sizeOverLifetime.enabled = true;
sizeOverLifetime.size = new ParticleSystem.MinMaxCurve(1f, AnimationCurve.Linear(0, 0.1f, 1, 1));

C

var sizeOverLifetime = ps.sizeOverLifetime;
sizeOverLifetime.enabled = true;
sizeOverLifetime.size = new ParticleSystem.MinMaxCurve(1f, AnimationCurve.Linear(0, 0.1f, 1, 1f));

D

var sizeOverLifetime = ps.sizeOverLifetime;
sizeOverLifetime.enabled = true;
sizeOverLifetime.size = new ParticleSystem.MinMaxCurve(1f, AnimationCurve.Linear(0, 1f, 1, 2f));

💡 Hint

Think about the size curve from 1 to 2 over the particle lifetime.

Option D enables size over lifetime and sets a linear curve from 1 to 2, making particles grow smoothly. Other options have wrong curve values or missing enabling.